This invention relates to a tractor/trailer combination comprising a tractor unit (e.g. a truck) and a trailer unit.
Coupling an undriven trailer to a truck or tractor causes an increase in the resistance to travel, without any compensation increase in tractive force. This can significantly reduce the ability of the tractor to traverse adverse grades or soft ground. It would therefore be desirable to be able to improve this ability by the addition of the trailer, rather than detracting from it.
The present invention provides a tractor/trailer combination comprising a tractor unit and a trailer unit, and continue means for automatically repeatedly forcibly increasing and forcibly decreasing the distance between the units in an alternating cycle at a predetermined frequency.
In one aspect the invention provides a tractor/trailer combination comprising a tractor unit, a trailer unit, and an extensible and retractable linear drive connecting the units, and control means for alternately extending and retracting the linear drive so as to alternately increase and decrease the distance between the units.
In another aspect the invention provides a method of assisting the progress of a tractor/trailer combination comprising a tractor unit and a trailer unit, the method comprising alternately forcibly increasing and forcibly decreasing the distance between the units.
The inventor has found that increasing and decreasing the distance between a tractor unit and a trailer unit in a series of pulses can have the advantageous effect that motion in the direction of travel (forward or reverse) is maintained, where it might otherwise be halted owing to the terrain. Alternatively, it is possible to increase the stroke length and move step-wise, the tractor unit and the trailer unit being stationary alternately.
The invention will be described further, by way of example, with reference to the accompanying drawings,: